This invention relates generally to medical devices, and more particularly to a catheter which can be formed, inside the human body, into a vast number of different shapes.
Selective catheterization of cerebral and visceral branch arteries is often difficult and at times impossible in some patients--particularly older patients with very tortuous and ectatic vasculature. Successful catheterization sometimes requires multiple catheter exchanges for various shaped catheters. It is not uncommon to easily catheterize three of four vessels for a four vessel head study, only to find that the fourth vessel (generally the left or right carotid) requires an entirely different catheter shape and tip orientation. It would be desirable if one could easily and simply reshape the catheter and reorient the tip to direct it into the vessel orifice, instead of depending on several complex catheters that require reformation, fancy torque and advancing maneuvers, body english and, above all, luck.
Tip reorientation, the goal of most prior devices which have addressed the problem, is only half of what is needed to make a truly workable universal catheter. Numerous catheter curve configurations have been conceived not only to reorient the tip properly for selection of branch vessels, but also to provide anchorage of the catheter against the aortic wall. A wide looped long tipped sidewinder III configuration with an exaggerated retrocurve is one such example of a highly specialized complex catheter.
This anchorage or wedge effect against the aortic wall lessens the recoil caused by the "jet effect" during high pressure contrast injection which might otherwise cause the catheter to flip out of the selected branch vessel (particularly in short branch vessels or at levels of a dilated aorta).
These complex configurations, therefore, evolved not only to orient the tip properly, but also to wedge the catheter securely in the branch vessel. Other devices which simply modify the distal catheter curve may aid in tip orientation for vessel selection, but fail to provide the anchorage which is necessary to prevent catheter dislodgement.
In addition, prior designs could be improved in that the radii which the prior devices are able to make (to enter a vessel at a sharp angle, for example) have heretofore been severely limited.
Moreover, the size of prior designs has made them less desirable for many applications.
In certain applications (for example, complex interventional procedures such as angioplasties or intracerebral procedures), current catheters could be improved with respect to their ability to facilitate crossing of tight stenoses or with respect to their trackability out into peripheral branches.
In this respect, the current catheters could be improved in the areas of displacing forces from the application site at the point of catheter introduction (most often in the inguinal area) to points close to the actual catheter tip. This would increase the control that a user, such as an angiographer, has on the catheter, creating a more precise local longitudinal vector force for crossing tight stenoses, and also increase torque force for guiding the catheter tip toward the orifice of a selected vessel.
In would also be desirable to have a catheter construction which provided controllable variability in the distal catheter stiffness. Such a catheter could be stiffened for support close to a first order selected branch through which a more flexible catheter could be tracked peripherally. Conversely, such a catheter could be made less stiff over variable distances to allow better tracking of a more flexible distal end over a guidewire.